Chapter 06

Chapter 6: Creating Custom Forms

Guide to Oracle 10g

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Global to this PPT: Please note that most figure slides have figure caption as slide title, not heading - okay? (The individual slides are commented.)

Guide to Oracle 10g 2

Lesson A Objectives

After completing this lesson, you should be able to:• Create and use custom forms• Create command buttons that use form triggers to

manipulate data• Use the Forms Debugger to find form logic and

runtime errors• Work with form triggers• Create form navigation triggers


Introduction to Custom Forms

• Custom form – Displays data fields from variety of database tables– Contains programs that support organizational

processes– Use lists of values (LOVs) to retrieve data values– Manipulate data using form triggers


Identifying the Business Processes and Database Operations

• Identify processes that form supports• Identify associated database tables• Describe process


Designing the Interface

• Visualize how form will look


Creating a Custom Form

• Manually create form canvas in Object Navigator• Create form items by “painting” items on canvas

– Using tools on Layout Editor tool palette• Write code that controls form functions


Creating the Form Canvas

• Manually create form canvas in Object Navigator• Start Forms Builder

– Create and rename form canvas– Rename form module and form window– Change Title property of form window

• Perform in Visual View in Object Navigator


Creating a Control Block

• Control data block– Also called control block– Data block not associated with particular database

table• Create new data block in Object Navigator

– Specify data block created manually– Use Ownership View


Creating the Form Items

• Create – Boilerplate logo image and text– Form text items – Command button items

• Display form in Layout Editor– Draw items on form canvas using tools in tool

palette


Creating the LOVs

• LOV– Retrieve data from database table

• Use LOV Wizard• Run form

– To test LOV


Displaying System Date and Time Values in Form Text Items

• System variable – Variable representing value always available to any

form• Display value in text item automatically

– Set text item’s Initial Value property


Forms Builder Date and Time System Variables

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Creating Command Buttons

• Create and configure buttons• Create form triggers associated with buttons


Creating and Configuring Command Buttons

• Draw button on canvas using Button tool – Button tool on tool palette

• Button group– Buttons should all be same size

• Wide enough to accommodate longest button’s label– Draw button with longest label first


Creating the Button Triggers

• Select Triggers node under button in Object Navigator– Click Create button to create trigger– Select trigger event– Specify trigger code

• WHEN-BUTTON-PRESSED button event– Trigger code executes when user clicks button


Creating the Button Triggers (continued)

• Reference form items:– :block_name.item_name

• Clear form text items in form trigger: – Use CLEAR_FORM built-in procedure– Create program unit to set value of text items to blank

text string• Procedure

– Code block that executes commands to change one or more values


Creating the Button Triggers (continued)

• Function– Code block – Returns single value

• Create program unit:– Open Object Navigator – Select Program Units node– Click Create button

• Program unit does not use DECLARE keyword


Using the Forms Debugger to Find Runtime Errors

• Runtime error – Error that does not keep program from compiling– Generates error while program running– Often result of user error

• Retrieve error messages associated with errors• Forms Debugger

– Step through triggers and other PL/SQL programs one line at a time

– Examine variable values during program execution


Retrieving FRM- Error Messages

• Investigate nature of error by looking up error code explanation– Oracle Technology Network (OTN) Web site

• FRM- prefix – Forms Builder error codes

• ORA- prefix – Generated by the DBMS


Using the Forms Debugger

• Click Run Form Debug button• Set breakpoint

– Pauses execution on specific program command– Examine current values of all program variables– Step through program commands to observe

execution path– Examine variable values to see how values change


Using the Forms Debugger (continued)

• Breakpoint – Pauses execution on specific command– Set on:

• Program lines that contain executable program commands

• SQL queries– To set:

• Double-click mouse pointer in gray shaded area on left side of PL/SQL Editor window


Using the Forms Debug Console

• Control form execution and examine form values• Buttons:

– Go– Step Into– Step Over– Step Out

• Execution arrow – Shows program line to execute next


Forms Debug Console

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Debug Console Windows

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Form Trigger Properties

• Trigger activated– In response to event such as clicking button

• Trigger name defines event that activates it


Trigger Categories

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Trigger Timing

• Specifies when trigger fires• PRE-

– Fire just before event successfully completes• POST-

– Fire just after event successfully completes• ON-,WHEN-, and KEY-

– Fire in response to actions


Trigger Scope

• Defines where event must occur in order for associated trigger to fire

• Includes object to which trigger attached– And objects within trigger object


Trigger Execution Hierarchy

• Defines which trigger fires – When object within form object contains same

trigger that form object contains• By default trigger in higher-level object overrides

trigger in lower-level object• Can specify custom execution hierarchy


Directing Form External Navigation

• External navigation – User causes form focus to change by making

different form item active• Form focus

– Item currently selected on form• Internal navigation

– Result of internal form code that responds to external navigation operations or trigger commands


Setting the Form Tab Order

• Set tab order – Place items in correct order under Items node

• In Object Navigator window


Directing External Navigation Using Built-in Subprograms

• Built-in subprograms– Called built-ins – Use to direct external form navigation

• Cannot use in navigational triggers


Built-in Subprograms to Control External Navigation

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Lesson A Summary

• Custom form – Displays data fields from variety of database tables – Processes data using triggers that contain SQL

commands• Runtime errors

– Errors that occur while form running• Forms Debugger

– Create breakpoints that pause execution


Lesson A Summary• Form triggers support:

– Block processing– Interface events– Master-detail processing– Message handling– Navigational events– Query processing– Transaction processing– Validation


Lesson B Objectives

After completing this lesson, you should be able to:• Suppress default system messages• Create alerts and messages to provide system

feedback to users• Create applications that avoid user errors• Trap common runtime errors


Controlling System Messages

• Forms Services message line– Displays FRM- and ORA- messages– Classified according to

• Severity• Whether or not they require user intervention

• Suppress default system messages – Replace with custom messages– Set :SYSTEM.MESSAGE_LEVEL variable

• In PRE-FORM trigger


Providing System Feedback

• Important application design principle – Provide users with feedback about what is

happening in application• Make applications forgiving

– Allow users to undo unintended operations


Custom Messages

• Short text string that displayed on form message line– Up to 200 characters

• Syntax:– MESSAGE('message_string');


Alerts

• Dialog box – Display text message longer than 200 characters– Displays one or more buttons

• Allow user to select between alternatives that execute associated program statements

• Top-level form object


Alerts (continued)

• Styles:– Note– Caution– Stop

• Button Label property determines:– How many buttons appear on alert – Labels on buttons– Maximum 3 buttons


Alerts (continued)

• To declare/display alert:DECLAREalert_button NUMBER;

BEGINalert_button:=

SHOW_ALERT('alert_name');END;


Example Alert

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Syntax to Display an Alert and Execute Alternate Commands

Depending on the Button the User Clicked

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Avoiding User Errors

• Help users avoid errors– Configure forms that validate input values – Programmatically disable form command buttons– Disable navigation for form text items containing

values that users should not change


Validating Form Input Values

• Validate input values– Ensure that values meet specific preset

requirements– Use

• Text item validation properties • Form validation triggers

• Validation unit– Represents largest chunk of data that user can enter

before form validates all input values


Text Item Validation Properties

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Validating Form Input Values (continued)

• Item validation trigger – Item-level trigger – Associate with item’s WHEN-VALIDATE-ITEM

event– Fires when item validated

• As determined by form validation unit– If not valid

• Raises built-in exception named FORM_TRIGGER_FAILURE


Disabling Form Command Buttons to Avoid User Errors

• Enable or disable button while form running:– SET_ITEM_PROPERTY('item_name', property_name, property_value);


Disabling Text Item Navigation

• Nonnavigable– User cannot press Tab key to place insertion point

in text item– Set item’s Keyboard Navigable property to No– User can still click mouse pointer in text item to

enter value• Create trigger that moves insertion point to another

form item• WHEN-MOUSE-UP event


Generating Runtime Errors

• Deliberately generate errors while updating and deleting records – View error messages


Trapping Form Runtime Errors

• ON-ERROR event occurs– Whenever ORA- or FRM- error occurs while form

running• Create form-level trigger that corresponds to ON-

ERROR event– Use decision control structure to handle different

errors


Forms Builder Built-in Procedures for Handling Errors

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General Syntax for an ON-ERROR Trigger

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Lesson B Summary

• Create custom messages and alerts – Provide feedback to users

• Validate user inputs using – Text item validation properties– Form validation trigger


Lesson C Objectives

After completing this lesson, you should be able to:• Convert data blocks to control blocks• Link data blocks to control blocks• Create a form that has multiple canvases• Create tab canvases• Create stacked canvases


Converting a Data Block to a Control Block

• Use Data Block and Layout Wizards to create data block form and form layout– Convert data block to control block– Add command buttons to control form processing– Simplify creation of control blocks


Converting a Data Block to a Control Block (continued)

• To convert data block to control block:– Change data block’s Database Data Block property

value to No– Change Required property value of text item that

represents data block table’s primary key to No


Linking a Data Block to a Control Block

• Create forms that link data blocks and control blocks to work together– Usually represent master-detail relationship


Creating the Data Block

• Use Data Block Wizard and Layout Wizards – To create and configure data block – Must contain field that links it to control block– Create data block without master-detail

relationship • Link two blocks later


Linking the Control Block and the Data Block

• Open detail data block’s Property Palette– Modify data block’s WHERE Clause property

• General syntax:– fieldname := control_block.text_item_name


Refreshing the Data Block Values

• Add commands to: – Initially populate data block display– Periodically refresh data block records

• Use the GO_BLOCK built-in:– To move form focus to data block

• Then execute EXECUTE_QUERY built-in– Flushes block– Makes information consistent with corresponding

database data


Creating Forms with Multiple Canvases

• Good practice not to show too much information on user’s screen display

• Single-form approach – Create one form with multiple canvases– Enables form to share data among different

canvases– Impossible for multiple programmers to work

simultaneously on different canvases of same application


Creating Forms with Multiple Canvases (continued)

• Multiple-form approach – Create multiple forms with different .fmb file for

each application canvas– Works well when multiple programmers

collaborate to create complex application– Enables programmers to use form in many

different applications– More difficult for related forms to share data


The Northwoods University Student Services Process

• Identify sequence of actions that user will employ to interact with canvases


Interface Design

• Student Log On canvas• Menu canvas• Student Information canvas• Course Grades canvas• Enrollment canvas


Working with Multiple Canvases and Data Blocks

• Create form that contains multiple canvases– Create individual canvases– Specify to display specific block items on specific

canvas• Create new data block

– Select canvas name on which block items appear • On Layout Wizard Canvas page


Working with Multiple Canvases and Data Blocks (continued)

• Often forms that have multiple canvases also have multiple data blocks– Group items that appear on same canvas in single

data block • To keep blocks small and manageable

– Cannot create two items that have same name in same data block

• Ensure that Forms Builder places new items in correct block


Specifying the Block Navigation Order

• Specify which canvas initially appears when user runs form– Canvas whose block items appear first under Data

Blocks node in Object Navigator window– Order of canvases in Object Navigator Canvases

list does not matter• Only order of data blocks


Object Navigator

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Referencing Different Canvases, Form Blocks, and Block Items

• All form items have Canvas property – Specifies name of canvas on which item appears

• Form always displays canvas on which item with focus appears

• Execute GO_ITEM built-in– Move form focus to item on target canvas– Good practice to include block name


Creating and Configuring Tab Canvases in Forms

• Tab canvases– Multiple-page canvases – Allow users to move between multiple canvas

surfaces • By selecting tabs at top of canvas

– Display large number of related items in modular way

– Direct user through sequence of steps for performing task


Creating a Tab Canvas

• Contains two or more tab pages• Tab page

– Object representing surface – Displays form items– Has tab label identifier at top


Creating a Tab Canvas (continued)

• Create form that contains tab canvas– Create form– Create new content canvas in form– Create tab canvas on content canvas– Configure tab pages


Creating Form Items on a Tab Canvas

• Use tab pages as any content canvas• Create items on tab pages

– Using Data Block Wizard– By creating control block and drawing text items

directly on tab canvases• Must be sure to specify placement of items on tab

canvas


Lesson C Summary

• Convert data block to control block• Create relationship between control block and data

block• Display information on multiple canvases:

– Single-form approach– Multiple-form approach

• Tab canvas – Multiple-page canvas


Summary

• Custom form • Runtime errors • Forms Debugger • Form triggers• Create custom messages and alerts • Validate user inputs

CE

I'm not sure if these last two slides (77 and 78) should be here. The summaries were included at the end of each lesson, so there is no need to include a complete summary like this at the end. Please note that all of the other PPTs have only the lesson summaries at the end of each lesson and not a complete summary like this at the end (w/the exception of ch3).


Summary (continued)

• Convert a data block to a control block• Create relationship between control block and data

block• Display information on multiple canvases• Tab canvas

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Chapter 06

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